The invention concerns a device for dispensing a prescribed product, agar in particular, into Petri dishes.
Petri dishes are small dishes of circular contour, in transparent plastic material, which contain a nutrient such as an agar medium; they serve as medium for the development of cultures containing micro-organisms and are used in large number by analytical laboratories, in particular for medical research and in industry. A dispensing device is known for example from document EP-B-385 902. This device comprises a rotating tray which, successively and step by step, brings open Petri dishes with their lid held distant above the bottom part, from a station supplying empty dishes to a filling station, then from this filling station to a receiving station of filled dishes, this tray comprising two coaxial, circular horizontal plates which are superimposed, each pierced with a series of corresponding circular openings, the openings of the upper plate having a smaller diameter than the lids but slightly larger than the diameter of the bottom parts to allow passing of the bottom parts whilst retaining the lids, a piston being provided to transfer an empty dish on the tray by placing its bottom part in the lower plate and retaining its lid in the upper plate, and another piston being provided to lift the filled bottom part from the bottom plate up into the lid retained in the upper plate.
This device has numerous drawbacks. The dish filling rate is of the order of one dish every 6 seconds according to the indication given in the document, which is relatively low. In addition, the opening time for each Petri dish is relatively long (about 16 seconds for a tray rotating by one notch every 4 seconds). Therefore, the risk of polluting the inside of the dish with undesirable particles is high.
Finally, in order to be able to fill the greatest possible number of dishes in minimum time, the device is relatively tall which generates access difficulties at the top of carousel for loading the stacks of empty dishes and removing the stacks of filled dishes. This problem is all the more detrimental since the persons using the device are mostly women who statistically are shorter than men.
Document FR-A-2 433 752 describes a device in which the Petri dishes are unstacked from the lower part of carousel towards a rotating tray with two superimposed plates. This rotating tray comprises three stations: a Petri dish unstacking station, a filling station via a tube and an elevating station using elevating means to move a filled dish up towards another stack of the carousel. This device also has the above-mentioned disadvantages.
Linear conveying devices are also known. U.S. Pat. No. 3,704,768 describes a Petri dish filling device comprising a conveyor performing a linear movement under a stack of empty Petri dishes towards a fixed part comprising two upper rails spaced apart by a smaller distance than two lower rails, the conveyor comprising a upper tray and a lower tray. In this device, a Petri dish is brought from the stack on the upper tray. Then, after recoiling leftwards, the tray is translated towards the right so that the upper rails retain the lid and the bottom of the dish falls onto the lower rails. Filling of the open bottom part is then carried out. Next, a forward vertical surface of the conveyor pushes the lid and filled bottom part to the left beyond the upper rails to cause the lid to fall onto the bottom part and push the dish onto a receiving table.
This device does not therefore produce stacks of filled Petri dishes, and the user must stack up the filled dishes. Also, the empty dishes must come up against a hook to lift off the lid during translation on the conveyor, which exerts an abutment force on the dishes and might cause damage thereto. Each filled dish arrives on a receiving table distant by a distance equal to the widths of three dishes relative to the stack of empty dishes. This device is therefore additionally very bulky.
Other linear, endless-belt conveyor devices are known from documents U.S. Pat. Nos. 4,468,914 and 5,698,260. These devices are even bulkier.
The invention sets out to obtain a device which overcomes the above-mentioned disadvantages by means of a device supplying a stack of filled Petri dishes from a stack of empty Petri dishes, which is of small bulk, which is able to provide a fast filling rate and has a large dish capacity whilst avoiding or reducing the risks of contamination of the dishes when they are opened.
For this purpose, a first subject matter of the invention is a device for dispensing a prescribed product into at least one Petri dish, each Petri dish comprising a removable lid able to be placed over a bottom part of smaller width than the lid, the device—on a base—comprising:
at least first and second columns for vertical guiding of the Petri dishes, capable of respectively receiving first and second stacks of Petri dishes with lids placed over the bottom parts and capable of being respectively positioned above a first lower passageway for Petri dishes and above a second lower passageway for Petri dishes, the first and second passageways being provided on a fixed part relative to the base,                a system to move at least one Petri dish from the first column to the second column, comprising:                    a transfer member having an upper opening supporting the lid of a Petri dish above a second lower opening supporting the bottom part of a Petri dish,            dispensing means to dispense said product above the lower opening into the bottom part of the Petri dish underneath the upper opening,            the mobile transfer member being capable of taking up a first stop position in which the supporting openings lie underneath the first passageway, and a second stop position in which the supporting openings lie underneath the second passageway,            a first piston comprising a first tray located under the first passageway and capable of passing through the openings to cause lowering of the lid and the bottom part of a Petri dish from the first column onto their respective supporting openings when the transfer member lies in the associated first stop position,            a second piston comprising a second tray located underneath the second lower passageway and capable of passing through the openings to raise the lid and the bottom part of the Petri dish from their respective supporting openings into the second column, when the transfer member lies in the associated second stop position,            wherein:                        the transfer member is a shuttle which moves in translation relative to the base, with direct back and forth movement of the supporting openings between each of the first and second stop positions,        the dispensing means being arranged to dispense said product above the lower opening and underneath the upper opening into the bottom part of the dish when these openings lie in a selected one of the first and second stop positions. With the invention no time is lost in bringing an open dish to a product filling station.        
In Embodiments of the Invention:                The device comprises synchronous driving means to drive the pistons to the same height.        The pistons are driven by the same motor.        The device comprises means for coordinating the translational movements of the shuttle and pistons so as to place them successively in the following positions:                    the first stop position with a lowered position of the first tray under the lower opening, to bring the lid of the dish onto the upper opening and to bring the bottom part of the dish onto the lower opening,            the second stop position, with the first tray under the lower opening for dispensing of product into the bottom part of the open dish positioned in the lower opening by the dispensing means,            in the second stop position, an elevation position lifting the second tray into the second column to close the lid over the bottom part of the dish and to transfer this closed dish to the second column,            the first stop position with a lowered position of the first tray underneath the lower opening.                        The dispensing means comprise an outlet nozzle for the said product, means for displacing the dispensing nozzle being provided to cause it to move between one and the other of a dispensing position of the said product in which the nozzle lies above the lower opening and under the upper opening in said selected stop position, and a retracted position in which the nozzle no longer lies between the openings, control means being provided to allow movement of the piston associated with the selected stop position only when the nozzle is in retracted position.        In addition to said supporting upper and lower openings, called second openings, the shuttle comprises means to support the bottom part of the Petri dishes which are provided with a first opening allowing the passing of the first piston in the first stop position.        In addition to said supporting upper and lower openings, called second openings, the shuttle comprises first upper and lower openings, the shuttle comprises a top-plate and an bottom-plate spaced apart by a prescribed distance to form a passageway for the dispensing means in dispensing position, the bottom-plate comprising the first lower opening—for passing of the first tray and first piston—and said second lower opening supporting the bottom part of the dish, the top-plate comprising a first upper opening—for passing of the first tray and first piston—and said second upper opening supporting the lid, the first upper opening being located above the first lower opening.        The device comprises means for raising the first tray and first piston to above the shuttle, the first tray is fixed to at least one lower rod linking the first tray with said lifting means, the shuttle comprises at least one communication passageway between the second openings and the first opening or first openings to allow the passing of said lower supporting rod when the shuttle is moved between the stop positions and the first tray is in raised position above the shuttle.        The device comprises at least one carousel mounted in rotation on a vertical axis of the base, the carousel comprising a plurality of columns for vertical guiding of the Petri dishes and each capable of receiving a stack of Petri dishes with lid placed on the bottom part, means for driving the carousel in rotation being provided to bring two of the columns respectively above the first lower passageway for the Petri dishes and above the second lower passageway to form said first and second columns.        The device comprises means for retaining and releasing the passing of Petri dishes above the second passageway, these retaining and releasing means being mobile between a first retaining position of the Petri dishes above the second passageway in the second column, and a second release position to allow passing of the Petri dishes in the second passageway, constraining means to constrain to the first retaining position being provided,                    means being provided for lifting the second tray and second piston as far as a prescribed elevation position in the second column,            the retaining means being arranged to be actuated in the second release position by abutment against said lid of the Petri dish when the second tray of the second piston carrying the dish of the associated lid is raised as far as the prescribed elevation position in the second column,            the retaining means, in the first retaining position, forming a passageway width that is narrower than the width of the bottom part of the Petri dish to give support thereto but which is wider than the width of the second tray of the second piston to allow its lowering under the second column.                        